There has been a considerable increase in sophisticated field research on various primates, but our growing quantitative information on primate sexual bahavior and its endocrine regulation has derived from laboratory studies of rhesus monkeys. However, the rhesus sexual pattern, both with regard to the male's and female's behavior is not typical of all primates nor even of the entire macaque genus. The proposed program will attempt to broaden the comparative scope of our knowledge of primate sexual behavior though systematic, parallel study of pigtail (N. nemestrina) and bonnet (M. mulatta) macaques, two species whose basic male and female patterns differ significantly. The program will include the study of the development of pigtail male sexual behavior (parallelling a previous study on bonnets) as well as studies of interspecific mating patterns. The primary investigations will detail the changes in sexual and related behaviors during the menstrual cycle of females of each species. This investigation will be followed by a sequence of studies using ovariectomized females, designed to assess the role of estrogen, progesterone and female adrenal androgen in regulating the sexual pattern of both the female and her partner. The overall behavioral focus will be directed at quantification of the specific components and sequencing of male and female behavior, the roles of female "attractiveness" and initiating "drive", and the means through which partner's specific stimulus characteristics regulates the sexual behavior of the dyad. These studies will be supplemented by studies of the development of sexually dimorphic social behaviors which may serve as the basis of adult socio-sexual patterns.